Technical Abstract:
Plant communities in desert environments are spatially anisotropic and nutrient islands develop below plant canopies that enhance plant growth and reinforce the spatial anisotropy. Catastrophic disturbance that removes the vegetation such as fire or drought can result in the release of the trapped sediment which becomes redistributed over the landscape by wind and water. We applied acid-dissolved Rare Earth Element (REE) tracers to different landscape positions of a desert ecosystem at the Sevilleta National Wildlife Refuge in central New Mexico. The area containing the plots was burned by U.S. Fish and Wildlife personnel and three grassland plots and three grassland-shrubland ecotone plots were tested by placing a portable boundary layer field wind tunnel over the plots and blowing them with 12 m s-1 wind for 10 minutes followed by a 30 minute test in which clean quartz sand abrader was added to the wind tunnel flow and a second test of 10 minutes with abrader added to the flow. Three paired aeolian sediment samples were collected for each plot tested. Sediment was extracted using 1N nitric acid and analyzed with ICP/MS. The results indicated that in desert grassland, a disproportionate amount of the post-fire sediment is entrained from areas under grass clumps and in grassland-shrubland ecotones, the soil under shrubs is the primary source of entrained sediment. The bare surfaces between vegetation produced the least sediment.